Download Mendel`s Laws of Segregation

Biology
HS/Science
Unit: 08 Lesson: 02
Mendel's Law of Segregation
Mendel's hypothesis has four essential parts:
1. “Alternative versions of genes account for variations in inherited characters.”
“This is the concept of alleles. Alleles are different versions of genes that impart the same
characteristic. Each human has a gene that controls height, but there are variations among these
genes in accordance with the specific height for which the gene "codes."
2. “For each character trait (such as height, color, texture etc.), an organism inherits two genes, one
from each parent.”
“This means that when somatic cells are produced from two gametes, one allele comes from the
mother, one from the father. These alleles may be the same (true-breeding organisms, e.g., ww and
rr) or different (hybrids, e.g. wr).”
©2012, TESCCC
05/14/13
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Biology
HS/Science
Unit: 08 Lesson: 02
3. “If the two alleles differ, then one, the dominant allele, is fully expressed in the organism's
appearance; the other, the recessive allele, has no noticeable effect on the organism's appearance.”
4. “The two genes for each character segregate during gamete production.”
This references meiosis, when the chromosome number changes from diploid to haploid (for
example, in humans from 46 to 23). “The two alleles of the organism are separated into different
gametes, ensuring variation.”
It was very important that Mendel observed traits that are inherited that do not have intermediate
forms because that was the leading biological theory during his time. This theory stated that inherited
©2012, TESCCC
05/14/13
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Biology
HS/Science
Unit: 08 Lesson: 02
traits blended from generation to generation. (Of course, there are exceptions to every rule. We know
now that some genes have incomplete dominance. In incomplete dominance, the dominant gene has
is not expressed completely, which results in a “mixed” phenotype.
Law of Independent Assortment
“The most important principle of Mendel's law of independent assortment is that the emergence of
one trait will not affect the emergence of another.” This means that offspring could have combinations
of genes that are not present in either the mother or father. For example, if a pea plant inherits green
seeds, this does not mean it will be more likely to also grow tall instead of short. In addition, this
principle explains why a human who inherits blue eyes rather than brown eyes does not make them
more or less likely to have the ability to roll their tongue or not. We now know that independently
assorted traits are found on different chromosomes, which explains this principle.
Quotations source:
Gregor Mendel. (2013, January 23). New World Encyclopedia. Retrieved 21:40, May 13, 2013 from
http://www.newworldencyclopedia.org/p/index.php?title=Gregor_Mendel&oldid=966503
©2012, TESCCC
05/14/13
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